Hybrid orientation scheme for standard orthogonal circuits

ABSTRACT

Embodiments herein present device, method, etc. for a hybrid orientation scheme for standard orthogonal circuits. An integrated circuit of embodiments of the invention comprises a hybrid orientation substrate, comprising first areas having a first crystalline orientation and second areas having a second crystalline orientation. The first crystalline orientation of the first areas is not parallel or perpendicular to the second crystalline orientation of the second areas. The integrated circuit further comprises first type devices on the first areas and second type devices on the second areas, wherein the first type devices are parallel or perpendicular to the second type devices. Specifically, the first type devices comprise p-type field effect transistors (PFETs) and the second type devices comprise n-type field effect transistors (NFETs).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.11/308,085 filed Mar. 6, 2006, the complete disclosure of which, in itsentirety, is herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments herein present a device, method, etc. for a hybridorientation scheme for standard orthogonal circuits.

2. Description of the Related Art

It is known that hole mobility is more than doubled on (110) siliconsubstrates with current flow direction along <110> compared withconventional (100) substrates. However electron mobility is the higheston (100) substrates. To fully utilize the advantage of the carriermobility dependence on surface orientation, CMOS devices have beenfabricated on hybrid substrates with different crystal orientations,with NFETs on silicon of (100) surface orientation and PFETs on (110)surface orientation with the NFET and PFET current flows both chosen tobe in <110> directions. High performance CMOS devices using 90 nmtechnology with physical gate oxide thickness as thin as 1.2 nm havebeen demonstrated. Significant PFET enhancement has been achieved.

SUMMARY OF THE INVENTION

Embodiments herein present device, method, etc. for a hybrid orientationscheme for standard orthogonal circuits. An integrated circuit ofembodiments of the invention comprises a hybrid orientation substrate,comprising first areas having a first crystalline orientation and secondareas having a second crystalline orientation. The first crystalorientation is (110) surface with the polysilicon gates aligned suchthat their source-drain directions are either (−11 sqrt(2)) or (1-1sqrt(2)) directions. Here the two gate orientations are orthogonal toeach other and have identical current flow directions. The secondcrystal orientation is (001) surface with (110) and (1-10) polysilicongate orientations. The first crystalline orientation of the first areasis not parallel or perpendicular to the second crystalline orientationof the second areas. The integrated circuit further comprises first typedevices on the first areas and second type devices on the second areas(each comprising the polysilicon gates), wherein the first type devicesare parallel or perpendicular to the second type devices. Specifically,the first type devices comprise p-type field effect transistors (PFETs)and the second type devices comprise n-type field effect transistors(NFETs).

Within the first area, the orthogonal gates are built such that thefirst type devices comprise a first direction current flow and a seconddirection current flow, wherein the first current flow is orthogonal tothe second current flow. A first carrier mobility of the first currentflow is equal to a second carrier mobility of the second current flow.The second area orthogonal gates are built such that the second typedevices also comprise a first direction current flow and a seconddirection current flow which have carrier mobilities that are equal.

Embodiments herein further comprise a method of forming an integratedcircuit, wherein the method attaches a first wafer having a firstcrystal orientation to a second wafer having a second crystalorientation such that the first crystal orientation is not parallel orperpendicular to the second crystal orientation. Next, the method etchesopenings within the first wafer and grows the second wafer through theopenings to create second wafer regions within the first wafer. Themethod then forms first type devices on the first wafer regions andsecond type devices on the second wafer regions. Specifically, formationof the first and second type devices comprises forming PFETs and NFETs.

Moreover, the second type devices are formed parallel or perpendicularto the first type devices. When attaching the first wafer, the firstwafer is attached to the second wafer at an angle such that the firsttype devices comprise a first current flow and a second current flow,wherein the first current flow is orthogonal to the second current flow.In addition, the method forms the first type devices with first andsecond current flows having a first carrier mobility and a secondcarrier mobility, respectively, wherein the first carrier mobility isequal to the second carrier mobility. Further, the method forms thesecond type devices again with first and second current flows havingidentical carrier mobilities.

Accordingly, the two in-plane orthogonal directions have the samemobility. They are in the (11 sqrt(2) and (11-sqrt(2)) directions. Whilethere is no direct measurement of the mobility of the current flows inthe (11 sqrt(2)) directions, it is reasonable to suggest that the holemobility value would lie between those of the <110> (100) and <110>(110) directions. Therefore, instead of the highly skewed 157% and 70%benefit for the two orthogonal directions of the prior art, embodimentsherein get approximately 110% benefit in both directions. This gives amajor structural opportunity to integrate orthogonally designedcircuits.

These, and other, aspects and objects of the present invention will bebetter appreciated and understood when considered in conjunction withthe following description and the accompanying drawings. It should beunderstood, however, that the following description, while indicatingembodiments of the present invention and numerous specific detailsthereof, is given by way of illustration and not of limitation. Manychanges and modifications may be made within the scope of the presentinvention without departing from the spirit thereof, and the inventionincludes all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the following detaileddescription with reference to the drawings, in which:

FIGS. 1A and 1B are graphs illustrating carrier mobility dependence onsurface orientation;

FIGS. 2A and 2B are diagrams illustrating semiconductor devices usinghybrid orientation technology;

FIGS. 3A, 3B, 3C, 4A, 4B, and 4C are diagrams illustrating method stepsfor forming semiconductor devices using hybrid orientation technology;

FIGS. 5A, 5B, 5C and 5D are diagrams illustrating surface and currentflow directions of a semiconductor device using hybrid orientationtechnology;

FIG. 6 is a diagram illustrating an integrated circuit; and

FIG. 7 is a flow diagram illustrating a method of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The present invention and the various features and advantageous detailsthereof are explained more fully with reference to the nonlimitingembodiments that are illustrated in the accompanying drawings anddetailed in the following description. It should be noted that thefeatures illustrated in the drawings are not necessarily drawn to scale.Descriptions of well-known components and processing techniques areomitted so as to not unnecessarily obscure the present invention. Theexamples used herein are intended merely to facilitate an understandingof ways in which the invention may be practiced and to further enablethose of skill in the art to practice the invention. Accordingly, theexamples should not be construed as limiting the scope of the invention.

Embodiments of the invention present two in-plane orthogonal currentflows having the same mobility. While there is no direct measurement ofthe mobility of the current flows, it is reasonable to suggest that thehole mobility value would lie between those of the <110> (100) and <110>(110) directions. Therefore, instead of the highly skewed 157% and 70%benefit for the two orthogonal directions of the prior art, embodimentsherein get approximately 110% benefit in both directions. This gives amajor structural opportunity to integrate orthogonally designedcircuits. There is a major concern with the many process knobs that areneeded to be optimized for integration. If the fall back is to go backto <001> surface devices for both NFET and PFET, then the ratio of thetwo orthogonal devices radically changes and circuit designs may fail.

The hybrid orientation scheme has been proposed (Yang et al., IEDM 2002)to leverage the best hole and electron mobility advantages. The electronmobility is highest on the (100) wafer surface while the hole mobilityis highest on the (110) surface as seen in FIGS. 1A-1B.

More specifically, the solid lines represent carrier mobility on the(110) wafer surface; the dotted lines represent carrier mobility on the(111) wafer surface; and, the dashed lines represent carrier mobility onthe (100) wafer surface. Therefore, Yang came up with the structure inFIGS. 2A-2B where the n-type field effect transistor (NFET) is done onthe (100) surface while the p-type field effect transistor (PFET) isdone on the (110) surface and the process for this is seen in FIGS. 3and 4. Specifically, FIG. 2A illustrates a PFET 20 on a (110)silicon-on-insulator 24 and an NFET 21 on a (100) silicon handle wafer25, wherein STI members 28 are on an upper portion of the (100) siliconhandle wafer 25. Moreover, FIG. 2B illustrates an NFET 22 on a (100)silicon-on-insulator 26 and a PFET 23 on a (110) silicon handle wafer27, wherein STI members 28 are on an upper portion of the (110) siliconhandle wafer 27.

Key Process Step Type A (FIG. 1A) Type B (FIG. 2B) layer transfer @bonding in (110) Si in (100) Si Selective Epitaxy grow (100) Si grow(110) Si

FIG. 3A illustrates thin oxide and nitride deposition, wherein a buriedoxide layer (BOX) 302 is formed on a silicon handle wafer 300, asilicon-on-insulator 304 is formed on the BOX 302 and a nitride layer306 is formed on the silicon-on-insulator 304. Next, middle portions ofthe nitride layer 306, the silicon-on-insulator 304, and the BOX 302 areremoved to form a gap 307, wherein spacers 308 are formed in the gap 307(FIG. 3B). The silicon handle wafer 300 is then epitaxially grown upthrough the gap 307 followed by chemical mechanical polishing (FIG. 3C).As illustrated in FIG. 4A, the nitride layer 306 is removed.

Next, standard shallow trench isolation is created between thesilicon-on-insulator 304 and the epitaxially grown portion of thesilicon handle wafer 300. The spacers 308 are also removed (FIG. 4B).Gate and spacer devices 310 are then formed over thesilicon-on-insulator 304 and the epitaxially grown portion of thesilicon handle wafer 300 (FIG. 4C).

FIGS. 5A and 5B show orientations of the gate for the NFET (100) andPFET (110) surfaces. FIG. 5C illustrates a top view of the gate, source,and drain areas. On the (100) surface for the NFET the current flow is<110> direction. On the (110) surface the hole mobility is highest inthe <110> direction (FIG. 5D). Yang proposes to align the gate in the(110) direction to get the maximum benefit. However, while it has thebest mobility gains it causes complications in circuit design. This isbecause the PFET device orthogonal to the <110> direction would have achannel current flow <100> direction. This makes the two devicesdifferent. In SRAMs and other logic circuits this causes an additionallayer of complexity in circuit design and limits the gate orientation.

Referring now to FIG. 6, embodiments of the invention comprise a hybridorientation substrate 600 having a notch 610, PFETs 620, and NFETs 630.The substrate 600 can represent either a type A structure, wherein thePFETs 620 are on a (110) silicon-on-insulator (i.e., a (110) crystallineoriented surface) and the NFETs 630 are on a (100) silicon epitaxiallayer (i.e., a (100) crystalline oriented surface); or a type Bstructure, wherein the NFETs 630 are on a (100) silicon-on-insulator andthe PFETs 620 are on a (110) silicon epitaxial layer (see FIG. 2).

Each of the PFETs 620 and each of the NFETs 630 comprise a source, adrain, a channel, and a gate (not shown). Extensions can be optionallyused. The source and the drain are heavily doped regions in thesubstrate 600, wherein majority carriers flow into the channel throughthe source and out through the drain. The channel is a high conductivityregion connecting the source and the drain, wherein conductivity of thechannel is controlled by the gate.

The PFETs 620 comprise current flows 621 and 622; and the NFETs 630comprise current flows 631 and 632. Specifically, the current flow 621is oriented in the <1-1 sqrt(2)> direction and the current flow 622 isoriented in the <−11 sqrt (2)> direction. The current flow 621 isorthogonal to the current flow 622.

The substrate 600 is formed by a layer transfer technique through waferbonding. First hydrogen is implanted into an oxidized silicon substratewith (110) orientation for type A or (100) orientation for type B. Thenthe wafer is flip-bonded to a handle wafer with different surfaceorientation. A two-phase heat treatment is then carried out to split thehydrogen implanted wafer and strengthen the bonding. Finally the top SOI(silicon-on-insulator) layer is polished and thinned down to the desiredthickness, for example, about 50 nm.

The process flow for CMOS fabrication on the hybrid substrate is shownin FIGS. 3 and 4. One additional lithography level is added to thestandard CMOS processes, which is used to etch through the SOI and theburied-oxide layer and expose the surface of the handle wafer. Theopened area should be for the NFETs 630 in the case of type A substrateor for the PFETs 620 for type B. Following a spacer formation, epitaxialsilicon is selectively grown through the opening by rapid thermalchemical vapor deposition. As a nature of epitaxy, this epi-silicon willbe in the same crystal orientation as the handle wafer. Defect-freesilicon epitaxial layers from both (100) and (110) handle wafers havebeen achieved. A defective interface between the epitaxial silicon grownfrom the SOI layer and the handle wafer will occur in case of spacerloss, which can be eliminated by improved processes. To avoid potentialproblems from facets due to the selective epitaxy, the epitaxial siliconthickness is adjusted to the point where the entire surface of theepitaxy layer is completely above the top surface of the thin nitride.Excessive silicon is then polished down by chemical mechanical polishing(CMP) to the thin nitride and etched back to level with the SOI surface.The additional lithography level used for silicon epitaxy in the NFET(or PFET) area is a large block level (several times larger than thecritical dimension), and is possible to be scaled beyond 45 nmtechnology node.

After removing the thin nitride and oxide, CMOS fabrication is continued(including both types of devices), including shallow trench isolation,well implants, gate oxide and polysilicon gate formations, spacer (oxideor nitride or multiple combinations thereof) formations, implants forjunctions formations (halos, extension, source/drain, etc.) silicideformation (can be Ni, Co, Pt, NiPt, NiPtRe, Pd, Ti, and other two or 3phase silicides) and metal contacts (W, Cu, etc.). Gate stacks arepatterned for the PFET to have a first current flow in the <1-1 sqrt(2)>direction (i.e., the current flow 610) and a second current flow in the<−11 sqrt (2)> direction (i.e., the current flow 620).

Accordingly, embodiments herein present an integrated circuit comprisingthe hybrid orientation substrate 600, including first areas having afirst crystalline orientation and second areas having a secondcrystalline orientation. The first crystalline orientation of the firstareas is not parallel or perpendicular to the second crystallineorientation of the second areas. For example, as discussed above, thefirst areas are on a (110) silicon-on-insulator (type A) or on a (110)silicon epitaxial layer (type B). Further, the second areas are on a(100) silicon epitaxial layer (type A) or on a (100)silicon-on-insulator (type B). The above HOT combinations with dual SOIand Direct Silicon Bonding for bulk are encompassed in embodiments ofthe invention.

The integrated circuit further comprises first type devices on the firstareas and second type devices on the second areas, wherein the firsttype devices are either parallel or perpendicular to the second typedevices. More specifically, the first type devices comprise PFETs 620and the second type devices comprise NFETs 630. As discussed above, eachof the PFETs 620 and each of the NFETs 630 comprise a source, a drain, achannel, and a gate. The source and the drain are heavily doped regionsin the substrate 600, wherein majority carriers flow into the channelthrough the source and out through the drain. The channel is a highconductivity region connecting the source and the drain, whereinconductivity of the channel is controlled by the gate.

Thus, embodiments herein leverage the best hole and electron mobilityadvantages. As discussed above, the electron mobility is highest on the<001> wafer surface while the hole mobility is highest on the <110>surface as seen in FIG. 1. Embodiments of the invention comprise thePFETS 620 on the <110> surface and the NFETS 630 on the <001> surface.

Additionally, the first type devices comprise a first current flow and asecond current flow, wherein the first current flow is orthogonal to thesecond current flow, and wherein a first carrier mobility of the firstcurrent flow is equal to a second carrier mobility of the second currentflow.

Embodiments herein further comprise a method of forming an integratedcircuit, wherein the method attaches a first wafer having a firstcrystal orientation (e.g., (110) silicon-on-insulator) to a second waferhaving a second crystal orientation (e.g., (100) silicon epitaxiallayer) such that the first crystal orientation is not parallel orperpendicular to the second crystal orientation. As discussed above, atwo-phase heat treatment is carried out to split the hydrogen implantedwafer (i.e., the first wafer) and strengthen the bonding. Due to thedifferent activation energy, (110) wafer requires a higher splittingtemperature. The top SOI (silicon-on-insulator) layer is polished andthinned down to the desired thickness, for example, about 50 nm.

Next, the method etches openings within the first wafer and grows thesecond wafer through the openings to create second wafer regions withinthe first wafer. As discussed above, to avoid potential problems fromfacets due to the selective epitaxy, the epitaxial silicon thickness isadjusted to the point where the entire surface of the epitaxy layer iscompletely above the top surface of the thin nitride. Excessive siliconis then polished down by chemical mechanical polishing (CMP) to the thinnitride and etched back to level with the SOI surface. The additionallithography level used for silicon epitaxy in the NFET (or PFET) area isa large block level (several times larger than the critical dimension),and is possible to be scaled beyond 45 nm technology node.

The method then forms first type devices on the first wafer and secondtype devices on the second wafer regions, wherein the second typedevices are formed parallel or perpendicular to the first type devices.Specifically, formation of the first and second type devices comprisesforming the PFETs 620 and the NFETs 630. As discussed above, each of thePFETs 620 and each of the NFETs 630 comprise a source, a drain, achannel and a gate.

Furthermore, when attaching the first wafer, the first wafer is attachedto the second wafer at an angle such that the first type devicescomprise a first current flow and a second current flow, wherein thefirst current flow is orthogonal to the second current flow. Forexample, the current flow 621 is formed oriented in the <1-1 sqrt(2)>direction and the current flow 622 is formed oriented in the <−11 sqrt(2)> direction. Furthermore, a first carrier mobility of the firstcurrent flow is equal to a second carrier mobility of the second currentflow. Therefore, as discussed above, embodiments herein leverage thebest hole and electron mobility advantages, wherein electron mobility ishighest on a <001> wafer surface while hole mobility is highest on a<110> surface.

FIG. 7 illustrates a flow diagram of a method of forming an integratedcircuit. In item 800, the method begins by attaching a first waferhaving a first crystal orientation to a second wafer having a secondcrystal orientation such that the first crystal orientation is otherthan one of parallel and perpendicular to the second crystal orientationa first wafer having a first crystal orientation to a second waferhaving a second crystal orientation such that the first crystalorientation is not parallel or perpendicular to the second crystalorientation. As discussed above, hydrogen is implanted into an oxidizedsilicon substrate with (110) crystalline orientation for type A or (100)crystalline orientation for type B. Then the wafer (i.e., the firstwafer) is flip-bonded to a handle wafer (i.e., the second wafer) withdifferent surface orientation.

Next, the method etches openings within the first wafer (item 810) andgrows the second wafer through the openings to create second waferregions within the first wafer (item 820). As discussed above, oneadditional lithography level is added to the standard CMOS processes,which is used to etch through the SOI and the buried-oxide layer andexpose the surface of the handle wafer. The opened area should be forthe NFETs 630 in the case of type A substrate or for the PFETs 620 fortype B. Following a spacer formation, epitaxial silicon is selectivelygrown through the opening by rapid thermal chemical vapor deposition. Asa nature of epitaxy, this epi-silicon will be in the same crystalorientation as the handle wafer. The growth rate of (110) silicon isslower than (100) silicon. A defective interface between the epitaxialsilicon grown from the SOI layer and the handle wafer will occur in caseof spacer loss, which can be eliminated by improved processes.

Following this, first type devices are formed on the first wafer (item830) and second type devices are formed on the second wafer regions(item 840), wherein the second type devices are formed parallel orperpendicular to the first type devices (item 842). The forming of thefirst type devices and the forming of the second type devices compriseforming transistors, specifically the PFETs 620 and the NFETs 630. Asdiscussed above, each of the PFETs 620 and each of the NFETs 630comprise a source, a drain, a channel and a gate. The source and thedrain are heavily doped regions in the substrate 600, wherein majoritycarriers flow into the channel through the source and out through thedrain. The channel is a high conductivity region connecting the sourceand the drain, wherein conductivity of the channel is controlled by thegate.

Furthermore, during the step of attaching the first wafer, the firstwafer is attached to the second wafer at an angle such that the firsttype devices comprise a first current flow and a second current flow,wherein the first current flow is orthogonal to the second current flow.For example, the current flow 621 is formed oriented in the <1-1sqrt(2)> direction and the current flow 622 is formed oriented in the<−11 sqrt (2)> direction. Moreover, the first current flow is equal tothe second current flow.

Accordingly, the two in-plane orthogonal directions have the samemobility. While there is no direct measurement of the mobility of thecurrent flows, it is reasonable to suggest that the hole mobility valuewould lie between those of the <110> (100) and <110> (110) directions.Therefore, instead of the highly skewed 157% and 70% benefit for the twoorthogonal directions of the prior art, embodiments herein getapproximately 110% benefit in both directions. This gives a majorstructural opportunity to integrate orthogonally designed circuits.There is a major concern with the many process knobs that are needed tobe optimized for integration. If the fall back is to go back to <001>surface devices for both NFET and PFET, then the ratio of the twoorthogonal devices radically changes and circuit designs may fail.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the invention that others can, by applyingcurrent knowledge, readily modify and/or adapt for various applicationssuch specific embodiments without departing from the generic concept,and, therefore, such adaptations and modifications should and areintended to be comprehended within the meaning and range of equivalentsof the disclosed embodiments. It is to be understood that thephraseology or terminology employed herein is for the purpose ofdescription and not of limitation. Therefore, while the invention hasbeen described in terms of preferred embodiments, those skilled in theart will recognize that the invention can be practiced with modificationwithin the spirit and scope of the appended claims.

1. An integrated circuit comprising: a hybrid orientation substrate,comprising first areas having a first crystalline orientation and secondareas having a second crystalline orientation; first type FET (FieldEffect Transistor) devices on said first areas of said substrate, saidfirst type FET devices having a channel length in a <1, −1, √2>direction; and second type FET devices on said second areas of saidsubstrate, said second type FET devices having a channel length in a <1,−1, √2> direction, wherein said first type FET devices comprise a firstcurrent flow and a second current flow, wherein said first current flowis orthogonal to said second current flow, and wherein a majoritycarrier mobility of said first current flow is equal to a majoritycarrier mobility of said second current flow.
 2. The integrated circuitaccording to claim 1, wherein said first type FET devices and saidsecond type FET devices comprise transistors.
 3. The integrated circuitaccording to claim 2, wherein said first type FET devices comprisep-type field effect transistors, and wherein said second type FETdevices comprise n-type field effect transistors.
 4. The integratedcircuit according to claim 1, wherein said first crystalline orientationis other than one of parallel and perpendicular to said secondcrystalline orientation.
 5. An integrated circuit comprising: a hybridorientation substrate, comprising first areas having a first crystallineorientation and second areas having a second crystalline orientation;first type FET (Field Effect Transistor) devices on said first areas ofsaid substrate, said first type FET devices having a channel length in a<1, −1, √2> direction; and second type FET devices on said second areasof said substrate, said second type FET devices having a channel lengthin a <1, −1, √2> direction, wherein said first crystalline orientationis other than one of parallel and perpendicular to said secondcrystalline orientation.
 6. The integrated circuit according to claim 5,wherein said first type FET devices and said second type FET devicescomprise transistors.
 7. The integrated circuit according to claim 6,wherein said first type FET devices comprise p-type field effecttransistors, and wherein said second type FET devices comprise n-typefield effect transistors.
 8. The integrated circuit according to claim5, wherein said first type FET devices are one of parallel andperpendicular to said second type FET devices.
 9. The integrated circuitaccording to claim 5, wherein an angle between said first crystallineorientation and said second crystalline orientation is such that saidfirst type FET devices comprise a first current flow and a secondcurrent flow, wherein said first current flow is orthogonal to saidsecond current flow.
 10. The integrated circuit according to claim 5,wherein said first type FET devices comprise a first current flow and asecond current flow, wherein a majority carrier mobility of said firstcurrent flow is equal to a majority carrier mobility of said secondcurrent flow.
 11. A method of forming an integrated circuit, comprising:attaching a first wafer having a first crystal orientation to a secondwafer having a second crystal orientation such that said first crystalorientation is other than one of parallel and perpendicular to saidsecond crystal orientation; etching openings within said first wafer;growing said second wafer through said openings to create second waferregions within said first wafer; forming first type FET (Field EffectTransistor) devices on said first wafer, said first type FET deviceshaving a channel length in a <1, −1, √2> direction; and forming secondtype FET devices on said second wafer regions, said second type FETdevices having a channel length in a <1, −1, √2> direction.
 12. Themethod according to claim 11, wherein said forming of said first typeFET devices and said forming of said second type FET devices compriseforming transistors.
 13. The method according to claim 11, wherein saidforming of said first type FET devices and said forming of said secondtype FET devices comprises forming p-type field effect transistors andn-type field effect transistors.
 14. The method according to claim 11,wherein said forming of said second type FET devices comprises formingsaid second type FET devices one of parallel and perpendicular to saidfirst type FET devices.
 15. The method according to claim 11, whereinsaid attaching of said first wafer comprises attaching said first waferto said second wafer at an angle such that said first type FET devicescomprise a first current flow and a second current flow, wherein saidfirst current flow is orthogonal to said second current flow.
 16. Themethod according to claim 11, wherein said forming of said first typeFET devices comprises forming said first type FET devices with a firstcurrent flow and a second current flow, wherein a majority carriermobility of said first current flow is equal to a majority carriermobility of said second current flow.
 17. A method of forming anintegrated circuit, comprising: attaching a first wafer having a firstcrystal orientation to a second wafer having a second crystalorientation such that said first crystal orientation is other than oneof parallel and perpendicular to said second crystal orientation;etching openings within said first wafer; growing said second waferthrough said openings to create second wafer regions within said firstwafer; forming first type FET (Field Effect Transistor) devices on saidfirst wafer, said first type FET devices having a channel length in a<1, −1, √2> direction; and forming second type FET devices on saidsecond wafer regions, said second type FET devices having a channellength in a <1, −1, √2> direction, wherein said attaching of said firstwafer comprises attaching said first wafer to said second wafer at anangle such that said first type FET devices comprise a first currentflow and a second current flow, wherein said first current flow isorthogonal to said second current flow.
 18. The method according toclaim 17, wherein said forming of said first type FET devices and saidforming of said second type FET devices comprises forming p-type fieldeffect transistors and n-type field effect transistors.
 19. The methodaccording to claim 17, wherein said forming of said second type FETdevices comprises forming said second type FET devices one of paralleland perpendicular to said first type FET devices.
 20. The methodaccording to claim 17, wherein said forming of said first type FETdevices comprises forming said first type FET devices with a firstcurrent flow and a second current flow, wherein a majority carriermobility of said first current flow is equal to a majority carriermobility of said second current flow.